title: Floral adaptation to local pollinator guilds in a terrestrial orchid.
abstract: OBJECTIVE
  Studies of local floral adaptation in response to geographically divergent pollinators are essential for understanding floral evolution. This study investigated local pollinator adaptation and variation in floral traits in the rewarding orchid Gymnadenia odoratissima, which spans a large altitudinal gradient and thus may depend on different pollinator guilds along this gradient.
  
  
  METHODS
  Pollinator communities were assessed and reciprocal transfer experiments were performed between lowland and mountain populations. Differences in floral traits were characterized by measuring floral morphology traits, scent composition, colour and nectar sugar content in lowland and mountain populations.
  
  
  RESULTS
  The composition of pollinator communities differed considerably between lowland and mountain populations; flies were only found as pollinators in mountain populations. The reciprocal transfer experiments showed that when lowland plants were transferred to mountain habitats, their reproductive success did not change significantly. However, when mountain plants were moved to the lowlands, their reproductive success decreased significantly. Transfers between populations of the same altitude did not lead to significant changes in reproductive success, disproving the potential for population-specific adaptations. Flower size of lowland plants was greater than for mountain flowers. Lowland plants also had significantly higher relative amounts of aromatic floral volatiles, while the mountain plants had higher relative amounts of other floral volatiles. The floral colour of mountain flowers was significantly lighter compared with the lowland flowers.
  
  
  CONCLUSIONS
  Local pollinator adaptation through pollinator attraction was shown in the mountain populations, possibly due to adaptation to pollinating flies. The mountain plants were also observed to receive pollination from a greater diversity of pollinators than the lowland plants. The different floral phenotypes of the altitudinal regions are likely to be the consequence of adaptations to local pollinator guilds.
authors.affiliation: Institute of Systematic Botany, University of Zürich, Zollikerstrasse 107, 8008 Zürich, Switzerland.
authors.forename: Mimi
authors.initials: M
authors.lastname: Sun
authors.forename: Karin
authors.initials: K
authors.lastname: Gross
authors.forename: Florian P
authors.initials: FP
authors.lastname: Schiestl
mesh_terms: D000222:Adaptation, Physiological; D000531:Altitude; D000818:Animals; D002241:Carbohydrates / Q000032:analysis; D017753:Ecosystem; D005060:Europe; D035264:Flowers / Q000033:anatomy & histology / Q000502:physiology*; D007313:Insecta / Q000502:physiology*; D009812:Odorants; D029595:Orchidaceae / Q000502:physiology*; D010858:Pigmentation; D057048:Plant Nectar; D054817:Pollination / Q000502:physiology*; D019655:Quantitative Trait, Heritable; D012098:Reproduction; D055549:Volatile Organic Compounds / Q000032:analysis
chemical_list: D002241:Carbohydrates; D057048:Plant Nectar; D055549:Volatile Organic Compounds
keywords: Diptera; Local adaptation; Orchidaceae; VOC; floral colour; floral evolution; floral morphology; floral scent; geographical variation; pollination; pollinator adaptation; pollinator assemblages; speciation